Current strategies to identify children at increased risk for premature atherosclerosis are based on the family history and selective screening for high blood cholesterol. These strategies are limited and fail to detect many children with high blood cholesterol. The goal of this research is to test a series of hypotheses regarding candidate biomarkers that may predict premature atherosclerosis. The candidate biomarkers include the genotypes for fibrinogen, angiotensin converting enzyme (ACE), lipoprotein lipase, the LDL receptor, and apoB and apoE isoforms. This is an observational longitudinal study of a cohort of 400 children and their parents. There is no intervention, treatment, or therapy, and no randomization. We will compare the frequency of the presence of candidate biomarkers in the families with and without early onset of the ischemic heart diseae. These comparisons will be done in groups of families in which the children have high blood cholesterol and also in groups of families in which the children have normal cholesterol levels.